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Involvement of FtsE ATPase and FtsX extracellular loops 1 and 2 in FtsEX-PcsB complex function in cell division of Streptococcus pneumoniae D39.

ABSTRACT: UNLABELLED:The FtsEX protein complex has recently been proposed to play a major role in coordinating peptidoglycan (PG) remodeling by hydrolases with the division of bacterial cells. According to this model, cytoplasmic FtsE ATPase interacts with the FtsZ divisome and FtsX integral membrane protein and powers allosteric activation of an extracellular hydrolase interacting with FtsX. In the major human respiratory pathogen Streptococcus pneumoniae (pneumococcus), a large extracellular-loop domain of FtsX (ECL1FtsX) is thought to interact with the coiled-coil domain of the PcsB protein, which likely functions as a PG amidase or endopeptidase required for normal cell division. This paper provides evidence for two key tenets of this model. First, we show that FtsE protein is essential, that depletion of FtsE phenocopies cell defects caused by depletion of FtsX or PcsB, and that changes of conserved amino acids in the FtsE ATPase active site are not tolerated. Second, we show that temperature-sensitive (Ts) pcsB mutations resulting in amino acid changes in the PcsB coiled-coil domain (CCPcsB) are suppressed by ftsX mutations resulting in amino acid changes in the distal part of ECL1FtsX or in a second, small extracellular-loop domain (ECL2FtsX). Some FtsX suppressors are allele specific for changes in CCPcsB, and no FtsX suppressors were found for amino acid changes in the catalytic PcsB CHAP domain (CHAPPcsB). These results strongly support roles for both ECL1FtsX and ECL2FtsX in signal transduction to the coiled-coil domain of PcsB. Finally, we found that pcsBCC(Ts) mutants (Ts mutants carrying mutations in the region of pcsB corresponding to the coiled-coil domain) unexpectedly exhibit delayed stationary-phase autolysis at a permissive growth temperature. IMPORTANCE:Little is known about how FtsX interacts with cognate PG hydrolases in any bacterium, besides that ECL1FtsX domains somehow interact with coiled-coil domains. This work used powerful genetic approaches to implicate a specific region of pneumococcal ECL1FtsX and the small ECL2FtsX in the interaction with CCPcsB. These findings identify amino acids important for in vivo signal transduction between FtsX and PcsB for the first time. This paper also supports the central hypothesis that signal transduction between pneumococcal FtsX and PcsB is linked to ATP hydrolysis by essential FtsE, which couples PG hydrolysis to cell division. The classical genetic approaches used here can be applied to dissect interactions of other integral membrane proteins involved in PG biosynthesis. Finally, delayed autolysis of the pcsBCC(Ts) mutants suggests that the FtsEX-PcsB PG hydrolase may generate a signal in the PG necessary for activation of the major LytA autolysin as pneumococcal cells enter stationary phase.

SUBMITTER: Sham LT

PROVIDER: S-EPMC3735124 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Involvement of FtsE ATPase and FtsX extracellular loops 1 and 2 in FtsEX-PcsB complex function in cell division of Streptococcus pneumoniae D39.

Sham Lok-To LT Jensen Katelyn R KR Bruce Kevin E KE Winkler Malcolm E ME

mBio 20130716 4

<h4>Unlabelled</h4>The FtsEX protein complex has recently been proposed to play a major role in coordinating peptidoglycan (PG) remodeling by hydrolases with the division of bacterial cells. According to this model, cytoplasmic FtsE ATPase interacts with the FtsZ divisome and FtsX integral membrane protein and powers allosteric activation of an extracellular hydrolase interacting with FtsX. In the major human respiratory pathogen Streptococcus pneumoniae (pneumococcus), a large extracellular-loo ...[more]

PMID: 23860769

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Project description:FtsEX is a membrane complex widely conserved across diverse bacterial genera and involved in critical processes such as recruitment of division proteins and in spatial and temporal regulation of muralytic activity during cell division or sporulation. FtsEX is a member of the ABC transporter superfamily. The component FtsX is an integral membrane protein, whereas FtsE is an ATPase and is required for the transmission of a conformational signal from the cytosol through the membrane to regulate the activity of cell wall hydrolases in the periplasm. Both proteins are essential in the major human respiratory pathogenic bacterium Streptococcus pneumoniae, and FtsX interacts with the modular peptidoglycan hydrolase PcsB at the septum. Here, we report high-resolution structures of pneumococcal FtsE bound to different nucleotides. Structural analysis revealed that FtsE contains all the conserved structural motifs associated with ATPase activity and afforded interpretation of the in vivo dimeric arrangement in both the ADP and ATP states. Interestingly, three specific FtsE regions with high structural plasticity were identified that shape the cavity in which the cytosolic region of FtsX would be inserted. The residues corresponding to the FtsX coupling helix, responsible for contacting FtsE, were identified and validated by in vivo mutagenesis studies showing that this interaction is essential for cell growth and proper morphology.IMPORTANCE Bacterial cell division is a central process that requires exquisite orchestration of both the cell wall biosynthetic and lytic machineries. The essential membrane complex FtsEX, widely conserved across bacteria, plays a central role by recruiting proteins to the divisome apparatus and by regulating periplasmic muralytic activity from the cytosol. FtsEX is a member of the type VII family of the ABC-superfamily, but instead of being a transporter, it couples the ATP hydrolysis catalyzed by FtsE to mechanically transduce a conformational signal that provokes the activation of peptidoglycan (PG) hydrolases. So far, no structural information is available for FtsE. Here, we provide the structural characterization of FtsE, confirming its ATPase nature and revealing regions with high structural plasticity which are key for FtsE binding to FtsX. The complementary binding region in FtsX has also been identified and validated in vivo Our results provide evidence on how the difference between the ATP/ADP-bound states in FtsE would dramatically alter the interaction of FtsEX with the PG hydrolase PcsB in pneumococcal division.

Dataset Information

Involvement of FtsE ATPase and FtsX extracellular loops 1 and 2 in FtsEX-PcsB complex function in cell division of Streptococcus pneumoniae D39.

Publications

Involvement of FtsE ATPase and FtsX extracellular loops 1 and 2 in FtsEX-PcsB complex function in cell division of Streptococcus pneumoniae D39.

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